Due to the adverse environmental conditions existing around drilling operations, drilling equipment is normally provided with operator cabs to separate the operator from the noise and dust of the drilling operations. Most drilling operations further require that drill extension rods be added to a drill string in order to enable the drill bit to reach a required drilling depth. When an operator is within a cab, he is unable to manually add drill rods to the drill string. Furthermore, in many drilling applications, the drill rod is too heavy for the operator to lift manually. These conditions have created the need for automated rod changing systems.
One type of presently existing automated rod changing system utilizes a separate rotating system to unthread the drill rod and coupling from adjacent drill rods in the drill string. These types of systems require a great deal of additional hardware causing the system to be very expensive. Other rod changing systems utilize the rotating system of a percussive drill to unthread the drill rod and coupling from the drill string. With these type of rod changing systems, the drill rod must be securely held while the percussive drill threaded element is threaded into the upper coupling on the drill rod. This operation enables the upper coupling, drill rod and percussive drill threaded element to rotate as a single element and unthreaded from the lower coupling when a drill rod is removed from the drill string.
After unthreading from the lower coupling, the upper coupling must be loosened from the percussive drill threaded element so that the drill rod and upper coupling can be moved to a storage area. Current designs in the industry use a separate break-out wrench to grip the upper coupling while the percussive drill threaded element is threaded or unthreaded from the coupling. The separate break-out wrench is mounted on the drill mast, feed-column, or the percussive drill mounting plate. In all of these cases, the extra break-out wrench assembly is expensive and requires additional maintenance for the drilling machine.
When the break-out wrench is mounted on the drill mast, the operator is also required to position the coupling in the area of the break-out wrench to perform the loosening operation. Another problem with current designs comes from the requirement of complicated, expensive components required to transfer the drill rod assembly from the drill string to the storage area. Therefore, a rod changing system incorporating more efficient methods for breaking loose threaded connections between drill rods and better capacities for transferring a drill rod between the drill string and a storage area is needed.